1. Field of the Invention
The present invention relates generally to botanical fumigant pesticides and, more specifically, to a botanical fumigant pesticide composition of matter made of plant essential oils containing secondary metabolites, and an apparatus and method for the controlled release of the botanical fumigant pesticide composition of matter.
2. Brief Description of the Related Art
Pests are undeniably a part of our life. Many pests are vectors of diseases and some are even deadly. With globalization and increased international travels, pests can easily disperse. Most pest control products focus on suppressing or eliminating the pest population once they are established with little attention to dispersal prevention.
Synthetic chemical pesticides have been globally used for pest control in the past few decades and, while they provided effective control, their widespread use have led to detrimental effects on human, animals and environment. Several pesticides have been proven to leave toxic, carcinogenic and harmful persistent residues in food, soil, ground water and the environment that can negatively affect humans, domestic animals, pollinators, birds and/or fish. Moreover, after many years of exposure, some pests can develop resistance to certain synthetic pesticides and gradually render them ineffective. In fact, regulatory guidelines in many countries have restricted the use of certain synthetic harmful pesticides. As a result of these regulatory restrictions, safe, effective and economical pest management has become a significant initiative.
In recent years, many new efforts have produced potentially less dangerous pesticides, many of which use botanicals as active ingredients, acting alone or in concert with conventional synthetic pesticides. Plant essential oils within the botanical category are of great interest as a safe alternative to synthetic pesticides due to their natural origin and toxicity. Derived from plants, many of them are considered safe to humans, animals and the environment. These essential oils have been used traditionally as healing medicines in many countries and ancient people were also aware of their pesticidal properties. However, only in recent years have these oils been commercialized as pest control products. Botanical biopesticides have several modes of action and act as toxins affecting a variety of receptors found in arthropods, for example, tyramine receptors (Ennan 2005), Octopamine receptors (Ennan 2001), GABA receptors (Priestly et al. 2009) and Acetylcholine receptors (Cavanagh et al. 2002). Many of the botanical essential oils tested on insects to date appear to have multiple modes-of-action and sites-of-action in the insect nervous system and elsewhere Osman et al. 2011). With rare exceptions, most botanical essential oils are non-toxic to humans and pets.
Plant essential oils are classified as plants' secondary metabolites and are, in general, complex mixtures of volatile and semi-volatile constituents. For instance, peppermint oil consists of several secondary metabolite constituents including menthol, menthone, methyl acetate, methofuran, isomenthone, germacrene-d, trans-sabinene hydrate and pulegone. The level of these constituents in the essential oils can vary based on the origin of the plants, the environmental conditions where the plants were grown, and the method that was used to obtain the essential oils.
Plant essential oils and their secondary metabolite constituents are readily obtained from plants utilizing simple processes including steam distillation, cold press and solvent extraction. These extraction processes and related science are applied to whole plant forms in large scale. Much of what is known from scientific studies about the pesticidal properties of these plant essential oils as contact toxicants is derived from analyses of their “whole plant” extracts. Some constituents of plant essential oils can also be obtained commercially in pure forms.
While plant essential oils and their constituents (secondary metabolites) do not have a primary role in metabolism of plants, they are valuable assets for plant defense, pollination and communication. Plant secondary metabolites are organic compounds that are not directly involved in the normal growth, development or reproduction of plants. Most plant secondary metabolites have defensive roles and plants actively use them as signaling agents. Most plants are capable of responding to changes in their surroundings and can convey precise information about their overall health status through those responses. Scientific studies (Miresmailli et al. 2012) of plant-arthropod interactions within the field of chemical ecology have revealed highly specialized processes of controlled release of synthesized combinations of a plant's secondary metabolites. These metabolites are either available as reservoirs in various parts of plants or synthesized de novo by plants when they need to use the metabolites to induce a behavior or send a signal. Many studies have looked at how plants synthesize, store, utilize and control the release of their secondary metabolites to manipulate their environment (i.e. induce repellency and attractant effects on behavior of pests and their natural predators; defend their vital organs through chemical antifeedants, etc.) (Schoonhoven et al, 2006). Most plants are capable of responding to changes in their surroundings and can convey precise information about their overall health status through those responses (Volkov et al. 2003). As an example, some plants are capable of showing the footsteps of insects crawling on their foliage (Bowen et al. 2002), while some other plants react to pest oviposition or feeding (Kessler et al., 2001). One of the well-documented responses of plants to biotic stressors is the emission of herbivore induced plant volatiles (HIPVs)—also known as info-chemicals (or semiochemicals) due to the fact that they carry some information about the status of the emitter. Plant semiochemicals (including plant secondary metabolites) can strongly affect the behavior of both predatory and herbivorous arthropods in nature and some plants are under strong selection pressure to release these volatiles. Various parts of plants, including leaves from both the abaxial and the adaxial side buds and roots, are known to emit HIPVs. The HIPVs are plant and pest-specific and the information they are conveying can change based on their composition and release rate.
When plants emit info-chemicals, they induce the desired action and behavior in the signal receiver. Some plants actively control the synthesis and release of these info-chemicals, both qualitatively and quantitatively. Many of the info-chemicals used in these plant communications are building blocks of plant essential oils (secondary metabolites). The same compounds that can trigger a behavior in one insect can kill another insect. Arthropods respond to specific mixtures of these volatile signals. Some plants are capable of actively changing the composition and release rate of their volatile chemical signals, and consequently changing the signal's intended message, and hence, the behavior or effect that is triggered.
Research performed by the inventors in biofuel crops confirms that plants actively control the composition and emission rate of the volatile organic compounds (secondary metabolites) that are emitted from different parts of their canopy. This research clearly established that these volatile signals play an important role in creating the biodiversity of arthropod communities in localized bioenergy agro-ecosystems—via both attracting and repelling specific arthropods.
Specific compositions and concentrations of botanical essential oil constituents (secondary metabolites) dictate the essential oil's specific attributes such as scent, taste, and viscosity as well as their pesticidal properties. Most of these constituents are the same low molecular weight chemicals as the volatile compounds that plants use for signaling and communication and, therefore, can easily volatilize out of the essential oils' matrix. Research performed by the inventors has shown that the presence of these constituents in a liquid mixture must be at certain levels for the efficacy of botanical essential oil-based pesticides to work as contact toxicants to control spider mites.
The tendency of pesticides based on botanical essential oils to breakdown before their full toxic effect is achieved is a known limitation for their use in applications where the environmental conditions can accelerate the breakdown process or where their application is such that pests can avoid contact while the active ingredients remain toxic. The present invention has mitigated this limitation by concentrating on inhalation toxicity where the rate of secondary metabolite volatilization is controlled.
Many pests have detoxification mechanisms with which they can break down the toxins and avoid mortality. While essential oils-based botanical pesticides have the capability of knocking down pests after short periods of exposure, the challenge is to achieve mortality by sufficiently long exposures and or higher concentrations to overcome the pests' initial adaptive strategies.
Fumigants enter the arthropod pest body through inhalation. In this case, it is not necessary for pests to come into direct contact with the pesticide in liquid form as is the case with sprays and foggers that are contact pesticides. Liquid contact toxicants can be rendered ineffective if pests manage to avoid physical contact with the liquid pesticide. If a fumigant is used inside confined spaces, the pests cannot escape from the deadly effects of the toxins in gaseous form that eventually reaches them via the air they breathe. It is impossible for the pests to build immunity to the fumigant pesticide. Several essential oils have fumigant capabilities as a result of their volatilization properties against arthropod pests. During the course of developing improved apparatuses and methods of fumigation, the inventors have found that various secondary metabolites of essential oils volatilize from the essential oil mixture at different rates. Heretofore unknown and unexpected is the ability to control differential volatilization rates of individual secondary metabolite constituents of botanical essential oils for use as fumigant pesticides, as opposed to controlling the breakdown rate of the essential oils as a liquid mixture when such mixtures are used as contact pesticides. The current invention controls volatilization rates and composition of secondary metabolite constituents of botanical essential oil-based pesticides in the air to achieve the durational toxicity and concentration needed for complete mortality of target pests in contained spaces and a very effective repellant where the space is not sufficiently contained.
In recent years, several technologies and concepts have been developed to control the release of pesticides and synergize their effect via special composition of active ingredients. These technologies, such as micro-encapsulation and pellet infusion, are designed to extend the release of pesticides in the air, water or other mediums. Extended release or synergy in these products is typically measured as a quantity with respect to concentrations of the active ingredients in their mixtures (e.g. a pesticide consisting of three essential oils), or quality with respect to specific blend of active ingredients in the mixture (e.g. mixing three different essential oils at different concentration) without measuring the durational persistence of individual constituents of each active ingredient (e.g. menthol and menthon in peppermint oil) that play fundamental roles in the active ingredient chemical, physical and biological attributes and consequently the efficacy of the pesticidal mixture. The present research revealed a heretofore unknown and unexpected significant improvement in the efficacy of botanical essential oil-based pesticide mixtures as fumigants achieved by focusing on controlling release at the level of individual secondary metabolite constituents that makeup essential oils used as active ingredients, rather than the more aggregate level of whole essential oils or whole mixture of essential oils. The current invention uses novel techniques for composing, fortifying and releasing toxic secondary metabolites to assure a sustained and efficacious toxicity level of individual active ingredients in essential oil-based fumigant pesticides and constituents thereof when used in gaseous form. An equally important aspect of the current invention disclosed herein is a method of controlling volatilization, which is inspired by plants' physiological, and biochemical defensive responses. The bio-inspired method allows consistent bioactivity of released volatiles of various essential oils listed on the United States Environmental Protection Agency's (EPA) 25(b) list and 4(a) list under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) when used a fumigant pesticides.
The present invention is designed to emulate the function of plants' info-chemical communication processes to control volatilization rates of specific secondary metabolites to achieve pesticidal effects. The present invention is intended to mimic the natural defensive mechanism of plants by acting via four distinct phases: (1) Initiation-Once exposed to air, the secondary metabolite compounds start volatilizing from the source and over a short time period they reach a certain volatilization rate and concentration that is sufficient to cause behavioral impacts if inhaled by the pests. (2) Repellence—At this phase, more volatiles are introduced into the air at levels sufficient enough to repel the pests which causes them to move away from the source of the formula. Pests naturally move as far as they can go from the source of chemicals. In the context of a moving box if the apparatus is placed inside the box on top of the content of the box, the pests will move towards the bottom of the box. Published scientific research and inventors' laboratory observations indicate that pests never move towards the source of chemicals. (3) Knockdown—At this phase, pests will be knocked-down and become immobile. The fumigant pesticide formula is a neurotoxin and, at very low concentrations, paralyzes the pests. At this stage, pests, though still alive, are located usually far from the source of toxic formula. The pests exhibit some mechano-reactions (e.g. shaking legs, shaking antenna) such that they are completely immobile but still breathing. (4) Confirm kill—At this phase, due to prolonged exposure to toxic volatiles and accumulation of volatile toxins in their body via breathing formula infused (toxic) air, the pests die.
The present invention, uses a complex array of multiple active components with different modes of action but a single mode of entry (e.g. inhalation). As a result, the detoxification mechanisms of pests cannot remove the respective toxins fast enough to revive themselves. The trade-off between detoxification of multiple toxins and keeping the vital organs alive is so high that the pest dies within a short period of time. It is important to note that pests will be repelled and paralyzed very quickly with minute concentrations of the fumigant but the “confirm kill” time may vary relative to the exposure time that is necessary to accumulate sufficient toxic materials inside the insect body via breathing. The accumulation time is correlated to the concentration of material in the airspace. It might take longer to kill “knocked-down” pests where the concentration of the material in the air is low (as a function of space volume). However, during this time, the pests will still be immobile and accumulating the toxic materials. Changes in the concentration of toxic fumigant materials in the airspace will not stop the killing process, rather it simply delays it. The process will continue as long as the toxic materials are infused in the air.
Volatilization research in pheromones, repellents and deterrents mostly focuses on the behavior that these compounds induce in the receiver (arthropods). Technologies used in these research areas (i.e. olfactometer, electroantennogram, etc.) correlate presence and level of certain volatiles to a measurable response in the target receiver. In these cases, the behavioral response is at the center of attention and the chemicals are used mainly to reproduce those behavioral responses. Materials are typically applied to a perfumery stick and placed in a device over which an air column can flow. The repellency or attractant result on target insects is then measured. However, these test methods cannot directly measure the amounts of volatilized material that is released from the liquid or solid form. They can only measure the weight of the material before and after to infer an amount theoretically volatilized, which is subject to error depending upon the sensitivity of the material to moisture uptake over the course of the testing process. The present invention allows fine-tuning the formula based on direct measurements of volatilization.
Another area of science related to volatilization research is trace gas analysis in atmospheric chemistry, air quality and global change studies. Several technologies are used to detect and monitor levels of specific gases in the air (i.e. Proton Transfer Reaction—Mass Spectrometer (PTR-MS)) that enables researchers to monitor specific compounds. This is a global inter-continental air quality measurement technology that is not applicable to the insect-pesticide world. In all these scientific endeavors, volatilization analysis is used either as an indicator of a substance's presence in liquid or solid form (as source of the volatile), thus confirmation of an induced behavior due to that substance presence in air or monitoring level of specific chemicals. Especially in the case of fumigant toxicity and repellent effects of volatiles, there is a gap of knowledge in understanding the behavior of volatile components when they transform from liquid form to gas form. Current methods enable researchers to determine the level of these components in liquid form (e.g. Gas Chromatograph-Mass Spectrometer (GCMS), Liquid Chromatograph-Mass Spectrometer (LCMS), High Performance Liquid Chromatography (HPLC)) and they can also record the ultimate effect (mortality, repellency, etc.) yet they cannot explain the specific relationship between these components in gaseous form and how these relationships might affect the final results.
The limitations of the prior art are overcome by the present invention as described below. The present invention focuses on this unexplored area using precision analytical methods to monitor temporal and special behavior of essential oils' secondary metabolite components in gaseous form and correlate that to their bio-impact on the test subjects over time. These novel methods and better understanding of the essential oils and their micro-components behavior in gaseous form has enabled the inventors to devise proprietary methods of controlling volatile compounds' action and manipulating their impact.
This unique methodology and invention allows the presented techniques/processes to scale predictably across a variety of enclosed man-made spaces and as such creates a new, efficient and effective pest control methodology. Plants' physiological structures for storing, mixing, and resource-conserving release methods provided a bio-inspiration for our invention. The present invention relies on the fundamental sciences of insect-plant interaction and plant info-chemical communication mechanisms to design environmentally safe, sustainable and efficacious pesticide products.